Daniel Ricciardo was nearly 40,000 feet above California when he made the huge decision to leave Red Bull and join Renault for 2019.

The Australian - winner of seven grands prix and arguably the best overtaker in the sport - had been agonising over a decision on his future for months. He chose a flight to Los Angeles at the start of his mid-season summer break last August to give him the clarity of mind he needed to decide on a move he knew would change his life.

His decision came as a surprise to F1 - Renault were often lapped by Red Bull last season, when Ricciardo won two races. Ricciardo, though, remains confident he knew what he was doing. He was aware then, as now, that he was likely to have to deal with a short-term drop in performance. The switch was about the long-term.

"The dream was getting this team back to winning," the 29-year-old said at a special event to which BBC Sport was invited at the Renault factory on the eve of the team's 2019 car launch on Tuesday.

For Renault themselves, signing Ricciardo was a no-brainer. It has sprinkled a little stardust on the team, and made a powerful statement of intent.

His presence has a double benefit - he's not only one of the best drivers in the sport, he's also without doubt the funniest; his fluorescent perma-smile and likeable personality make him a ray of human sunshine.

The excitement as Ricciardo addressed the team in the room where the cars are prepared for races was palpable.

"I'm stoked; I really am. I feel part of the team already," he said at the start of a short but typically disarming and amusing speech, his charisma lighting up the room.

Team boss Cyril Abiteboul says: "It has been a huge boost, a huge motivation. It could also be a spark, because I think we have put a lot of right ingredients in three years - people, resources, investment - but at some point you need something to ignite the mixture and that is what I hope is coming from Daniel."

Why Ricciardo went to Renault

Renault have a proven pedigree in F1, having won many world titles as an engine supplier - with Williams and Benetton in the 1990s, and Red Bull in the early 2000s - and two drivers' and constructors' doubles with Fernando Alonso in 2005 and '06.

But that's more than a decade ago, and the last few years have been hard. They pulled out of F1 as a team owner at the end of 2009, and re-entered for 2016, buying back the team they used to own, which had been allowed to fall into something close to disrepair after years of under-investment by its previous owners.

The target then - as now - was to be taking podiums by 2020 and winning races by 2021. Signing a superstar driver, it is hoped, is one of the last pieces of the jigsaw.

Looking back on his big decision at six months' distance, Ricciardo says there has not been a moment's doubt about what he has done.

"I walked on the plane, thinking: 'This is what I am going to do, but I still wasn't sure'," he said. "On the flight is where I was: '100%, this is it'. And I never turned back from there."

Ricciardo is aware many have questioned the decision - how could a driver take such an apparently obvious backward step, some wondered?

Now faced with the reality of his decision, Ricciardo says it still feels like the right thing to have done.

"It really does," he says. "You're right - if I really didn't feel it, I would probably try and make up something. But it did feel right. And hand on heart, it does feel right. The process of making the decision was stressful, but once I had made the call, I was, like, instantly de-stressed and that hasn't changed."

Part of Ricciardo's motivation was seeing how Lewis Hamilton's career has progressed since he left McLaren at the end of 2012 to join Mercedes. That was another decision that was questioned at the time, for similar reasons, but Hamilton has since gone from having one world title to five, from 20 wins to 73.

"What Lewis did at Mercedes, there's definitely part of that, yeah, inspires me," says Ricciardo. "If I was able to do that here, I wouldn't complain."

Baku crash part of why he left

As for the motivation for leaving Red Bull, many have presumed it was because team-mate Max Verstappen finally established clear superiority in their private battle last year.

Ricciardo says there were myriad reasons, and admits one was to do with Verstappen - if not necessarily what many might think.

He says he was not impressed with the way the team dealt with the crash at last year's Azerbaijan Grand Prix that took out both drivers after an intense and often wheel-banging battle for two-thirds of the race.

Ricciardo rammed Verstappen from behind - but only after the Dutchman had done a double defensive move that is strictly forbidden in the rules.

"I didn't want to hold a grudge on that," Ricciardo says. "I couldn't tell you how many pieces made up the kaleidoscope but I guess that was one of the little pieces.

"I mean, we both got a talking to, putting it politely. In my eyes, I guess the incident itself, I felt like I was not really in the wrong, even if I'm the one that hit him. I think most people saw the double move.

"Before that there was a lot of contact, and a lot of people thought it went on too long. I guess the way it was handled at the time didn't sit too well with me.

"Handling the media, I get. It's a big brand to look after. I get it doesn't help if we both go off at each other. But I felt there was a bit of equal blame (from the team). And maybe it's just me being a stubborn race car driver but I didn't think it was an equal incident, is the easiest way to put it.

"So that was a little thing, I guess, which bothered me. But it wasn't the deal-breaker."

Aspirations at Renault

Ricciardo's arrival has put Renault's other driver, Nico Hulkenberg, somewhat in the shade, and team insiders say the German has struggled with that a little over the winter, after three seasons becoming used to being their main man.

It would be wrong, though, to assume Ricciardo will have it all his own way. No less a figure than Alonso has regularly referred to Hulkenberg as one of the most talented drivers on the grid, saying it was only because he had lacked decent machinery that he had yet to score a podium.

Going against Ricciardo is a chance for Hulkenberg to prove he is deserving of such praise, and he is well aware of the opportunity.

"It will be interesting to see if he kicks my ass or not," say Hulkenberg, who might lack Ricciardo's cheery personality, but has a nice line in sardonic humour when the mood takes him. "It's great to have a seven-time grand prix winner. It's definitely a good comparison and really interesting."

Both drivers talk about Renault's ambition for 2019 being "progress" - consolidation of the fourth place they achieved last year.

But Ricciardo says he is under no illusions about being behind his former team when the new season starts at his home race next month.

"I was aware when I signed the deal here that it was very realistic they are going to be in front, come Melbourne," he says. "Naturally I am going to look at them. But I am also going to look at Mercedes and Ferrari as well. I am not going to be bitter if they beat us in Melbourne. I feel now we are still on a different journey but I don't want to settle for fourth forever."

As for what he has seen of Renault in the short time he has been there, Ricciardo says: "I think there are enough resources to get into that world. I don't think that's unattainable for us. It might not be this year, but it's not a permanent handicap.

"Since 2016 it has been pretty awesome what they've done, to keep going in that trajectory. Saying 'you got fourth last year, you've got to get third this year' - it's not that simple, because the gap to the top is pretty big. But, you know, ideally we just close that gap. If it does jump us into the top three, all well and good, but as long as we make inroads, that has got to be a pretty successful year."

Abiteboul adds: "Since three years it's clear we have had a nice and steady progression and I don't want to see anything that kills that. We don't want to see anything jeopardising that momentum.

"It is fair to say more progress in the championship will take a bit longer. We are humble and professional enough to recognise that. But it is important to get some glimpses that our ambitions are correct."

Hopes of more power

Abiteboul says much of his hope for a step forward this year rests on the engine, an area in which Renault have struggled since the turbo hybrid V6s were introduced in F1 in 2014.

Last year, Renault were in danger of slipping to fourth best of the four engine manufacturers on the grid, after progress from Honda, which now supplies Red Bull. But Abiteboul says the engine department in Viry-Chatillon near Paris "have had in particular a very strong winter". Progress, he says, has been "substantial".

"The furthest I will go is to say it is the biggest step we have made since the V6 introduction. But then it is how fast we are compared to the others and I don't know what the others will have done."

The grapevine suggests Renault have found 35kw (46bhp) gain in qualifying trim and 20kw (27bhp) in the race. If so, this would put them close to the level Mercedes and Ferrari were at in 2018, although no-one thinks the top two won't find more performance over the winter.

As for the car, he says: "On the chassis side, we have the structure but it is going to take a bit of time before the structure can turn into a race-winning car."

'Speed takes time'

As Abiteboul leads a tour of the factory, his pride at the results of Renault's investment in the last three years, reflected in the growth of the site and the new high-tech equipment in many rooms, is matched only by his anxiety about how up-against-it the team are to get the car ready for the start of pre-season testing next week. They've "never been so late" he says.

"For (the start of testing on) Monday, we should be fine," he says, "but we have a (private) filming day on Saturday, and for that…" his voice tails off and he puts his thumb under his chin and pushes his head up, as if to say they are struggling to keep their heads above water.

For those who work at Renault, the progress the team has made is stark.

In the operations room, where high-speed data transfer enables a team of engineers in the factory to work in concert in real time with those at the track, is head of vehicle performance Chris Dyer. It is a name some might recognise from his time as Michael Schumacher's race engineer during Ferrari's domination of the early 2000s.

Dyer, who lost his job at Ferrari in the wake of the strategic misjudgement in Abu Dhabi in 2010 that cost Alonso the title in his first year with the team, was one of the first new signings at the Renault factory at Enstone in Oxfordshire at the start of the new era. He says it has been "an amazing transformation - very dramatic".

Back in the lobby, alongside Alonso's title-winning car, Renault have commissioned a small exhibit from an up-and-coming Parisian artist. The theme, he says, is "speed takes time".

It's an effective aphorism for Renault's journey back to the top.

After building the foundations of success, they are looking for reassurance this season that while their time might not be now, it will not be too far away.

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